Computer controlled defibrillator

ABSTRACT

A computer controlled defibrillator comprising a set of electrodes which are engageable with a patient and which are connected to a source of electrical energy by a circuit means. The circuit means comprises storage capacitors, energy selector, computer, manual and reset switches, voltage monitor, current monitor, and output meter. The computer responds to certain external inputs, automatic and manual, and controls the output delivered to the patient. The energy selector permits the selection of the energy which is desired to be delivered to the patient. The sequence is started by closing the manual reset switch which zeroes the output meter and activates the power supply (electrical energy) at a voltage which is dependent on the energy selector. The energy derived from the power supply is stored in the storage capacitors. The energy selector, which is manually set to the energy desired, also feeds an input to the computer. When the manual switch is activated, the computer causes the stored energy source to be connected to the patient through the electrodes. The current monitor and voltage monitor feed instantaneous signals to the computer which computes the energy as a continuous integration process. When the computed energy equals the selected energy, the computer causes the energy source to be disconnected from the patient. The total energy delivered to the patient is indicated as a steady reading on the output meter. A modified form of the defibrillator is also disclosed wherein the magnitude of current in the electrical circuit means may be manually or automatically selected to enable the defibrillator to compensate for the patient&#39;&#39;s body weight or body resistance.

[451 Jan. 14, 1975 COMPUTER CONTROLLED DEFIBRILLATOR Inventors: DavidBell, 1804 N. 111th St.;

William K. Hagan, 12418 Leavenworth St., both of Omaha, Nebr. 68154Filed: Mar. 13, 1974 Appl. No.: 450,792

Related U.S. Application Data Continuation-in-part of Ser. No. 420,291,Nov. 29, 1973, which is a continuation-in-part of Ser. No. 219,455, Jan.20, 1972, Pat. No. 3,782,389.

U.S. Cl 128/419 D Int. Cl A6ln 1/36 Field of Search 128/419 D, 419 R,419 P,

[56] References Cited Primary Examiner-William E. Kamm Attorney, Agent,or Firm-Zarley, McKee, Thomte & Voorhees [57] ABSTRACT A computercontrolled defibrillator comprising a set of electrodes which areengageable with a patient and which are connected to a source ofelectrical energy by a circuit means. The circuit means comprisesstorage capacitors, energy selector, computer, manual and resetswitches, voltage monitor, current monitor, and output meter. Thecomputer responds to certain external inputs, automatic and manual, andcontrols the output delivered to the patient. The energy selectorpermits the selection of the energy which is desired to be delivered tothe patient. The sequence is started by closing the manual reset switchwhich zeroes the output meter and activates the power supply (electricalenergy) at a voltage which is dependent on the energy selector. Theenergy derived from the power supply is stored in the storagecapacitors. The energy selector. which is manually set to the energydesired, also feeds an input to the computer. When the manual switch isactivated, the computer causes the stored energy source to be connectedto the patient through the electrodes. The current monitor and voltagemonitor feed instantaneous signals to the computer which computestheenergy as a continuous integration pro cess. When the computed energyequals the selected energy, the computer causes the energy source to bedisconnected from the patient. The total energy deliv ered to thepatient is indicated as a steady reading on the output meter. A modifiedform of the defibrillator is also disclosed wherein the magnitude ofcurrent in the electrical circuit means may be manually or automaticallyselected to enable the defibrillator to compensate for the patients bodyweight or body resistance.

3 Claims, 9 Drawing Figures Pmimzmmmms 3.860.009

SHEET em 5 JUIKNGRM l l QE,

PAIEN E JAN 1 4mm saw 3 or 5 NQQ NKMQ o N PATENIEDJANWBYS 3,860,009

SHEET OF 5 @afiw sum/1? a 30 e COMPUTER CONTROLLED DEFIBRILLATORBACKGROUND OF THE INVENTION This application is a continuation-in-partapplication of the application Ser. No. 420,291 filed Nov. 29, 1973which was a continuation-in-part application of the application Ser. No.219,455 filed Jan. 20, 1972, now US. Pat. No. 3,782,389.

The use of DC defibrillators in emergency resuscitation has become wellestablished. Limitations due to weight have prevented more widespreaduse of the defibrillators. Most clinical defibrillators depend on thestorage and discharge of energy through a stable RLC combination, thusrequiring accurate capacitance, inductance and resistance. Theconventional defibrillators employ a pair of electrodes or paddles whichare placed in contact with the patients chest. A defibrillation orelectrical pulse is then applied to the patient, through the electrodes,to momentarily stop the heart so that fibrillation of the heart isstopped. Since time is critical in defibrillation techniques, it isextremely important that a sufficiently large impulse be applied to thepatient during the first attempt. A majority of the prior art devicesemploy some means for selecting the energy to be delivered to thepatient. However, it has been found that these devices generally delivera smaller or lower output to the patient than that which was selected. Afurther complication is that the resistance of the patients varygreatly. Thus, the operator could possibly determine that it wasnecessary to apply an impulse of 200 joules to the patient. Quite often,the variances in the defibrillator and the variable resistance of thepatient will result in considerably less than 200 joules being appliedto the patient. If the pulse is insufficient to momentarily stop thepatients heart, the patient could possibly die.

Research has indicated that there is a possible correlation between thebody weight or body resistance of the patient and the electrical current(energy doses necessary to defibrillate a fibrillating heart). Inapplicants previous defibrillator, the amount of energy delivered to thepatient was measured and used as a control to insure that the deliveredenergy is equal to the energy selected to be delivered. In applicantsprevious defibrillator, the amount of current was not controlled butfixed.

Therefore, it is a principal object of this invention to provide animproved defibrillator.

A further object of this invention is to provide a defibrillator whereinthe energy delivered to the patient substantially equals the selectedenergy.

A further object of this invention is to provide a defibrillatorincluding a circuit means having an energy computer and control whichcomputes the energy delivered to the patient and causes the energysource to be disconnected from the patient when the computed energysubstantially equals the selected energy.

A further object of this invention is to provide a defibrillator whichdelivers the selected energy to the patient regardless of the resistanceof the patient.

A further object of this invention is to provide a defibrillatorincluding a resistance monitor which measures the body resistance of thepatient and automatically selects the current amplitude of the energydelivered to the patient.

A further object of the invention is to provide a defibrillator whereinthe magnitude ofcurrent can be manually or automatically selected.

A further object of the invention is to provide a defibrillator havingmeans for manually or automatically selecting the magnitude of currentresponsive to the patients body weight or body resistance.

A further object of the invention is to provide a method ofdefibrillating a fibrillating heart.

A further object of this invention is to provide a defibrillator whichis economical of manufacture, durable in use and refined in appearance.

These and other objects will be apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of thedefibrillator of this invention:

FIG. 2 is a block diagram of the electrical circuitry of thedefibrilltor:

FIG. 3 is a block diagram illustrating the components of the energycomputer and control and its relationship with other components of thedevice:

FIG. 4 is a schematic view of a portion of thc cir cuitry of theinvention:

FIG. 5 is a schematic view of more of the circuitry of the invention:

FIG. 6 is a schematic view of more of the electrical circuitry of theinvention:

FIG. 7 is a block diagram similar to FIG. 3 except that the means formanually controlling the magnitude of current in the circuit means isillustrated:

FIG. 8 is a block diagram similar to FIGS. 3 and 7 except that anautomatic means is disclosed for controlling the magnitude of current inthe electrical circuit means; and

FIG. 9 is a block diagram similar to FIGS. 7 and 8 except that aresistance monitor is shown.

DESCRIPTION OF THE PREFERRED EMBODIMENT With respect to FIGS. 1 6, thedefibrillator of this invention is referred to generally by thereference numeral 10 and comprises a portable housing 12 having a pairof electrodes or paddles l4 and 16 connected to the circuitry therein aswill be described in more detail hereinafter. The electrodes or paddlesl4 and 16 are engageable with the patient to deliver a predeterminedenergy output to the patient to momentarily stop the patients heart sothat fibrillation of the heart is stopped.

The circuitry of the defibrillator is depicted in sche' matic form inFIG. 2 wherein the numeral 18 refers to a l 10 VAC power supply having aswitch 20 associated therewith. The power supply 18 is electricallyconnected to the storage capacitors 22 which are adapted to store energyderived from the power supply 18. A switch mechanism 24 is connected tothe storage capacitors 22. Mechanism 24 is connected to the electrodesl4 and 16 as seen in FIG. 2 and to voltage monitor means 26 and currentmonitor means 28. Manual switch 30 and reset switch 32 are connected tothe energy computer and control means 34 as is the output meter 38.Energy selector 36 may be comprised of a conventional rotatable dial orthe like for setting the energy to be delivered to the patient.

The energy computer and control means 34 is illustrated in schematicform in FIG. 3. In FIG. 3, it can be seen that the current monitor 28and voltage monitor 26 are electrically connected to the Multiplier 40and that the Multiplier 40 is connected to an Integrator 42. Integrator42 is connected to an Analog Memory 44 which is connected to the meter38. The current monitor 28 and the voltage monitor 26 are also connectedto a Time Out Comparator 46 which is connected to the OR gate 48. Theenergy selector 36 is connected to the Time Out Comparator 46, IntegralComparator 50 and Voltage Comparator 52. The Integral Comparator 50 isconnected to the OR gate 48 and to the Integrator 42 as depicted in FIG.3. Voltage Comparator 52 is connected to the Voltage Reference 54 and tothe Charge Logic 56. The Multiplier 40 is also connected to the VoltageComparator 52.

The reset switch 32 is electrically connected to the Analog Memory 44and to the Charge Logic 56 which the manual switch 30 is connected tothe Delay-Start 58 and to the Charge Logic 56.

The heart of the control mechanism in the defibrillator is the energycomputer and control 34 which responds to certain external inputs,manual and automatic, and controls the output delivered to the patient.In operation, the manual reset 32 starts the sequence by zeroing theoutput meter 38 and activating the power supply 18 at a voltage which isdependent on the energy selector 36. Thus, if it were desired to deliveran impulse of 200 joules to the patient, the energy selector 36 would beset at 200 joules. The energy derived from the power supply 18 is storedin the storage capacitors 22. The energy selector 36, which is manuallyset to the energy desired, also feeds an input to the energy computerand control 34. The electrodes or paddles 14 and 16 are then placed intocontact with the patient and the manual switch 30, located on either orboth of the paddles l4 and 16, is activated.

When the manual switch 30 is activated, the energy computer and control34 causes the stored energy source to be connected to the patient. Thecurrent monitor 28 and voltage monitor 26 feed instantaneous signals tothe energy computer and control 34 which computes the energy as acontinuous integration process. When the computed energy equals theselected energy, the energy computer and control 34 causes the energysource to be disconnected from the patient. The total energy deliveredto the patient is indicated as a steady reading on the output meter 38.

More specifically, the circuitry of FIGS. 4, and 6 operates as follows.The circuit of FIG. 4 is basically the power supply for the device. TP3transformer feeds a full wave bridge rectifier to generate plus andminus DC voltage. The transistor and zener diodes regulate the DC to iv. and are of conventional design. The second set of diodes leading tothe coils of K1 and K2 supply power to operate these relays. Contact K3operates coil K2. K2 operates the contacts on FIG. 5. K3 is operated offthe control circuit illustrated in FIG. 6. These devices, K2 and K3,control the main discharge from the firing circuit to the patient. K2connects the patient to the measuring circuit during the time that thedefibrillator is not being fired.

Kl which is controlled by the voltage comparator 52 and charge logic 56switches 110 VAC to transformers T1 and T2. This circuit supplies powerto the capacitor bank 22 in FIG. 5 as required to maintain 1,400 VDC.

The four rectifiers between T1 and T2 in FIG. 4 and the four capacitors22 in FIG. 5 form two full wave voltage double circuits in cascade togenerate 1,400 v. About 500 joules of energy are then stored in the capacitor bank. Initially all four silicone controlled rectifiers SCR arenot conducting. The 150 K resistors around the SCRs are used to balancethe off leakage current. The 0.05 mfd 50 ohm networks around each SCRare to suppress switching transcients.

Terminals l, 2 and 3 are the monitor points. The voltage between 1 and 2is proportional to the stored voltage and the voltage to the load. Thevoltage between 1 and 3 is proportional to the current in the load. The5 ohm, watt resistor serves the dual'function of current shunt andcrow-bar protection.

The remainder of this circuit can be best explained by a typicaloperating sequence. Initially the capacitors are charged and all SCRsare off. The cycle starts with the start input going to a positive 15 v.This starts the 0.030 sec. timer 58. At the same time K2 relay begins toclose. The timer delay is to allow K2 to close completely. When theunijuncti'on transistor in the timer fires, a large current pulse is fedto trigger transformers T1 and T2. These pulses turn on SCR 1 and 2applying power to the load. The LED is turned on by the applied voltageand is optically coupled to the photo transistor in FIG. 6. Thistransistor starts timeout comparator Z9. When the comparator circuitdetermines the required energy has been delivered, a positive voltage isapplied to the stop terminal. This fires the small 2N5062 SCR generatinga high current pulse in T3 and T4. This pulse fires SCR 3 and 4 whichcrow-bars the remaining energy in the capacitor bank.

With respect to FIG. 6, amplifiers Z1, Z2 and Z3 form two DCdifferential amplifiers. These amplifiers convert the essential floatinginputs 1, 2 and 3 to ground referenced signals. The two outputs are v(t)from Z2 and i(t) from Z3. These signals are fed to 40 which togetherwith Z4 form an analog multiplier. The output of Z3 in mathematicalterms is V (t) x i (l)/K.

This signal is proportional to the power being delivered to the load atany instant of time. Z5 is an integrator which integrates power withtime to give energy. The AC coupling network on the output of Z3 removesthe long term DC drift. The output at this point is approximately anincreasing ramp voltage. This ramp'is compared to the setting of thepotentiometer 36, by comparator 50. When these are equal, the comparatorsends the stop output high. The peak value of the ramp is stored on the0.22 mfd capacitor in analog storage circuit 44. The four transistoramplifier has a gain of +1. This allows the energy delivered to bedisplayed on the meter.

Comparator Z9 (46) performs a similar function to 50 except it comparesthe potentiometer 36 setting with time. In this way the output pulsewidth is limited to a maximum value for any given setting. This circuitdoes not affect operation for loads of less than ohms.

Comparator Z6 controls the charging of the capacitor bank. Z6 comparesthe output of amplifier Z2 which is proportional to the bank voltage toa zener diode. A certain amount of positive feedback is used ascontrolled hysteresis to prevent chatter of relay K1.

The remaining transistors are used as switches to turn on or off certainfunctions when the manual switch 30 is closed. For example, the voltagecomparator Z6 is turned off and comparators 56 and 50 and analog memory44 are turned on.

FIGS. 7, 8 and 9 are block diagrams similar to FIG. 3 except that meansfor controlling the magnitude of current in the circuit means isillustrated. With respect to FIG. 7, the numeral 100 refers to avariable voltage control of the manual type which is electricallyconnected to the voltage reference 54. The variable voltage control 100may be a manually controlled adjustable resistor, switch or the like.The circuitry of FIG. 7 operates in the same manner as the circuitryillus trated in FIG. 3 except that the control 100 is provided formanually controlling the amount of current in the defibrillator. Theoperation of the circuitry of FIG. 7 is as follows. The operator wouldinitially determine the amount of energy to be delivered to the patientand would determine the approximate body weight of the patient. Thevariable voltage control 100 would then be manually adjusted in responseto the approximate body weight of the patient. In the circuitry of FIG.3, it was only necessary to determine the energy to be delivered to thepatient since the current in the circuitry of FIG. 3 is not variable butis fixed. The manual reset 32 starts the sequence by zeroing the outputmeter 38 and activating the power supply 18 at a voltage which isdependent upon the energy selector 36. Thus, if it had been determinedthat it was desirable to deliver an impulse of 200 joules to thepatient, the energy selector 36 would be set at 200 joules. The energyderived from the power supply 18 is stored in the storage capacitors 22.The energy selector 36, which is manually set to the energy desired,also feeds an input to the energy computer and control 34. Theelectrodes or paddles 14 and 16 are then placed into contact with thepatient and the manual switch 30, located on either or both of thepaddles l4 and 16, is activated.

When manual switch 30 is activated, the energy computer and control 34causes the stored energy source to be connected to the patient. Thecurrent monitor 28 and voltage monitor 26 feed instantaneous signals tothe energy computer and control 34 which computes the energy as acontinuous integration process. When the computer energy equals theselected energy, the energy computer and control 34 causes the energysource to be disconnected from the patient. The total energy deliveredto the patient is indicated as a steady reading on the output meter 38.

As previously stated, the voltage reference 54 is variable which resultsin the output of the voltage comparator 52 and charge logic 56 to resultin a variable charge voltage on the energy storage capacitors 22 in FIG.2. Since the amount of current is proportional to the voltage, thedesired current can be selected by manually selecting the referencevoltage 54 by means causes a suitable variable voltage control which maybe a switch or variable resistor.

It is also possible to control the reference voltage with the energyselector 36 through a proper sealer such as seen in FIG. 8 so that ashigher energy levels are selected, corresponding higher values ofcurrent are supplied automatically. FIG. 8 is identical to FIG. 7 exceptthat a sealer 102 has been substituted for the variable voltage controland is electrically connected to the energy selector 36 in conventionalfashion as seen in FIG. 8. Sealer 102 may comprise an amplifier having again of A which may be greater than or less than 1. Thus, the referencevoltage 54 is controlled with the energy selector 36 through anamplifier or proper scaler so that as higher energy levels are selected,corresponding higher values of current are supplied automatically to thesystem.

The circuitry illustrated in FIGS. 7 and 8 may be substituted for thecircuitry of FIG. 3 in the defibrillator so that the magnitude ofcurrent therein can be manually or automatically selected since thereappears to be a correlation between the patients body weight and theeurrent-energy doses necessary to defibrillate a defibrillating heart.

It is also possible to control the reference voltage with the resistancemonitor 103 as seen in FIG. 9 so that as the patients body resistanceincreases, the corresponding higher values of current are suppliedautomatically. FIG. 9 is identical to FIG. 7 except that a re sistancemonitor 103 has been substituted for the variable voltage control.

The resistance monitor comprises a high impedance oscillator 104 whichsupplies a source of signal at a frequence of approximately K Hz to thepatient load through the paddles l4 and 16. The signal that is sup pliedis a conventional high impedance, constant current source such that thesignal current through the patient is constant and is not effected bythe variation of patient body resistance. Since the current is constant,the voltage across the patient load is directly proportional to theresistance of the patient. The amplilier 105 increases the level of thesignal so that it can be rectified in 106. The resultant DC signal willbe directly proportional to the body resistance. Thus the referencevoltage 54 is controlled by the resistance monitor 103 so that as thebody resistance increases, corresponding higher values of current aresupplied automatically to the system.

Thus it can be seen that the defibrillator accomplishes at least all ofits stated objectives.

We claim:

1. A defibrillator comprising in combination,

an electrical power source,

a set of electrodes engageable with a patient,

circuit means connecting said power source to said set of electrodescomprising, a computer means, a storage capacitor means for storingenergy derived from said power source, an energy selector means forselecting the energy to be delivered to the patient, said energyselector means also feeding an input to said computer means, a switchmeans for causing the stored energy to be connected to the patient, saidswitch means being operatively elcc trically connected to said computermeans, a power monitor means for feeding signals to said computer meanswhen said stored energy is delivered to the patient, said computer meanscomputing the energy delivered to the patient and causing the deliveryof energy to the patient to be discontinued when the computed energysubstantially equals the selected energy,

said circuit means also comprising means for selecting the magnitude ofcurrent delivered to the patient responsive to the body resistance ofthe patient.

2. The defibrillator of claim 1 wherein said means for selecting themagnitude of current comprises a resistance monitor means.

3. The defibrillator of claim 2 wherein said electrical circuit meansincludes a reference voltage means and wherein said resistance monitormeans is electrically connected to said reference voltage means and tosaid

1. A defibrillator comprising in combination, an electrical powersource, a set of electrodes engageable with a patient, circuit meansconnecting said power source to said set of electrodes comprising, acomputer means, a storage capacitor means for storing energy derivedfrom said power source, an energy selector means for selecting theenergy to be delivered to the patient, said energy selector means alsofeeding an input to said computer means, a switch means for causing thestored energy to be connected to the patient, said switch means beingoperatively electrically connected to said computer means, a powermonitor means for feeding signals to said computer means when saidstored energy is delivered to the patient, said computer means computingthe energy delivered to the patient and causing the delivery of energyto the patient to be discontinued when the computed energy substantiallyequals the selected energy, said circuit means also comprising means forselecting the magnitude of current delivered to the patient responsiveto the body resistance of the patient.
 2. The defibrillator of claim 1wherein said means for selecting the magnitude of current comprises aresistance monitor means.
 3. The defibrillator of claim 2 wherein saidelectrical circuit means includes a reference voltage means and whereinsaid resistance monitor means is electrically connected to saidreference voltage means and to said set of electrodes.